This invention relates to a system for generating an image of a space and to a system for projecting a previously acquired image.
There are many applications for systems which can generate a wide angle or panoramic image of a space from a single camera. Such applications include surveillance systems, and surveying and cinematography.
International patent application No. PCT/AU94/00501 (publication no. WO 95/06303) by the present applicant discloses a panoramic imaging system utilising a single camera and a dome like convex mirror. In one arrangement, the camera is mounted with respect to the mirror such that most of the mirror surface is within the field of view of the camera and the mirror surface has a profile which directs radiation from the space to the image plane of the camera. In another arrangement, the camera is embedded in the dome like mirror and a second mirror reflects radiation from the first mirror surface to the image plane of the camera. The disclosure of International patent application no. PCT/AU94/00501 is incorporated in this specification by cross-reference.
A difficulty with the earlier system is that the area of the space occluded by the camera, or by the secondary reflector used when the camera is mounted within the mirror, occludes part of the space to be imaged. The size of the occluded area increases with increasing distance from the mirror surface. That is, the size of the xe2x80x9cblind zonexe2x80x9d to the camera increases with increasing distance from the surface. A further difficulty is that the occlusion results in an image of the imaging device itself appearing usually at the centre of the image. This image does not contain information and reduces the area available for the non-occluded region of space.
It is an object of this invention to provide a system for generating an image of a space which will overcome, or at least ameliorate one or more of the foregoing disadvantages.
It is a secondary object of this invention to provide a system for projecting a previously generated image of a space.
Accordingly, in a first aspect, this invention provides a system for generating an image of a space, said system including camera means having an image plane and a field of view, a reflective surface positioned within the field of view of said camera and configured to reflect radiation from said space onto the image plane of said camera, said camera occluding radiation from being received at said reflective surface from an area of said space, and said reflective surface being configured such that said occluded area is of substantially constant or decreasing area with increasing distance into said space from said reflective surface.
In a second aspect, this invention provides a system for generating an image of a space, said system including camera means having an image plane and a field of view, a reflective surface configured to reflect radiation from said space onto a secondary reflector positioned in the field of view of said camera and configured to reflect incident radiation from said reflective surface onto the image plane of said camera, said secondary reflector occluding radiation from an area of said space from reaching said reflective surface and said reflective surface being configured such that said occluded area is of substantially constant or decreasing area with increasing distance into said space from said reflective surface.
In a third aspect, this invention provides a system for projecting an image into a space said system including means to direct light representative of said image onto a reflective surface, said reflective surface being configured to reflect said light into said space in a pattern which generates said image in said space, said means to direct light occluding light from being reflected from said reflective surface into an area of said space and said reflective surface being configured such that said occluded area is of substantially constant or decreasing area with increasing distance into said space from said reflective surface.
In a fourth aspect, this invention provides a system for projecting an image into a space said system including means to direct light representative of said image onto a secondary reflector configured to reflect incident light onto a reflective surface, said reflective surface being configured to reflect said light into said space in a pattern which generates said image in said space, said secondary reflector occluding light from being reflected from said reflective surface into an area of said space and said reflective surface being configured such that said occluded area is of substantially constant or decreasing area with increasing distance into said space from said reflective surface.
Preferably, the reflecting surface or primary mirror is circularly symmetric. Preferably, the primary mirror has a generally concave central portion surrounded by a generally convex portion in turn surrounded by a further generally concave portion. The camera is mounted on the axis of the circularly symmetric mirror. In the first aspect of the invention, the camera is directed at the primary mirror. In the second aspect of the invention, the camera is aligned with an aperture in the primary mirror formed around the optical axis and the secondary reflector directs radiation reflected by the primary mirror onto the image plane of the camera as described above.
Preferably, the image of the third and fourth aspects of the invention is an image generated using the systems of the first and second aspects of the invention respectively. That is, the principle of reversibility of light is used to project a previously recorded image of a space into a space with the pattern of light having the same angular distribution.
Preferably, the means to direct light representative of the image onto the reflective surface of the third and fourth aspects of the invention include a transparency through which light from an approximated point source is directed.
In one form of the invention, a discontinuity can be formed in the primary mirror surface or in the secondary reflector surface to prevent imaging of the occluded area.
The primary mirror and/or secondary reflector (where used) can provide optical gain where required.
It will be apparent that the system of this invention provides for minimal occlusion of the area being imaged and optionally for ensuring the imaging device is not visible in the output image. Additionally, the invention provides a system that allows the generated image to be projected through the same set of optics to provide a panoramic projection system.
Some embodiments of the invention will now be described, by way of example only.